A two dimensional 1-bit receptor array has been described as a digital-film sensor (DFS), which is an array of deep-SDL (sub-diffraction-limit) pixels, defined as those smaller than a 550 nm Airy disk diameter, wherein each pixel is a fraction of a micron in size. While several photoelectrons could contribute to pushing the output signal above some threshold, ultimately single photoelectron sensitivity is said to be desired. It is said that a pixel that only needs to detect a single photoelectron has much lower performance requirements for full-well capacity and dynamic range than an analog pixel in a conventional image sensor. These specialized pixels have been referred to as “jots”.
The implementation of a jot may be by making a conventional active pixel with very high conversion gain (low capacitance). Other approaches are said to include using avalanche or impact ionization effects to achieve in-pixel gain, as well as the possible application of quantum dots and other nanoelectronic devices. It is stated that stacked structures are also possible.
In operation, at the start of the exposure period the jot would be reset to a logical ‘0’. If it is then hit by a photon during exposure the jot is set to a logical ‘1’ immediately or upon readout. Due to the single-bit nature of the “analog-to-digital” conversion resolution, it is said that high row-readout rates can be achieved.
It is said that color can be handled in a manner analogous to current color image sensors. That is, the jots could be covered with color filters. In this case red (R), green (G) and blue (B) jots could be treated separately, and later the digitally developed images combined to form a conventional RGB image. It is said that R, G, and B jots need not appear at the same spatial frequency.
Typical technologies for generating color images rely on the Bayer sensor and its variations. Other techniques include the use of color wheels and prisms. FIG. 1 shows a typical Bayer-type pattern having a combination of RGB filter elements. The use of more G filter elements than R or B filter elements is to mimic the greater resolving power of the human eye to green light. Other filter types include, by example, CYGM filters (cyan, yellow, green magenta) and RGBE filters (red, green, blue, emerald). It is also known to use a transparent or white filter element to provide infrared sensitivity.